Automated phasing device for phasing wheel attachment bolts and methods utilizing same

ABSTRACT

An automatic wheel attachment apparatus for attaching a wheel to a wheel attachment member of an automotive body. The automatic wheel attachment apparatus includes a reorienting device for reorienting a wheel attachment surface of the wheel attachment member, a phasing device for phasing wheel attachment bolts on the wheel attachment member, the phasing device being movable longitudinally and vertically of the automotive body to bring the wheel attachment member and the phasing device into central alignment with each other, a detecting device for detecting the amount and direction of movement of the phasing device, and a nut runner for fastening the wheel to the wheel attachment member while the center of the wheel attachment member as detected by the detecting device is being held in alignment with the center of the wheel. At least the reorienting device, the phasing device, and the detecting device are combined in a single robot. The automatic wheel attachment apparatus also includes a wheel gripping device for gripping the wheel with at least three gripping fingers under equal forces, and a wheel positioning device for positioning the wheel before it is brought into a wheel attachment position.

This is a divsional of application Ser. No. 53,263 filed May 22, 1987,now U.S. Pat. No. 4,841,632.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an automatic wheel attachment apparatusfor automatically attaching wheels to an automotive body, and moreparticularly to a robot in such an automatic Wheel attachment apparatusfor reorienting a wheel attachment member or hub, phasing wheelattachment bolts on the wheel attachment member, and positionallydetecting the wheel attachment member.

2. Description of the Relevant Art

One conventional apparatus for automatically mounting wheels on anautomotive body is disclosed in Japanese Laid-Open Patent PublicationNo. 60-42521 published Mar. 26, 1985.

The disclosed automatic wheel attachment apparatus includes a robotmounted on an attachment base and movable transversely (X direction),longitudinally (Y direction), and vertically (Z direction) of theautomotive body by respective driver mechanisms. The robot is alsoswingable to meet the toe-in angle (θ) and the camber angle (γ) of ahub. The robot is thus singly capable of performing various phases ofoperation ranging from the detection of the hub position to theattachment of a wheel to the hub.

In the conventional apparatus, the wheels are installed on theautomotive body with the hubs (automotive body) used as a positionalreference, except when the hub bolts are phased. Therefore, the robotmust be angularly moved in the X, Y, Z directions and also in directionsto 5 meet the toe-in angle (θ) and the camber angle (γ). As a result,the apparatus requires a total of six control axes about which the robotshould rotate, resulting in a complex mechanism and a lower degree ofreliability.

SUMMARY OF THE INVENTION

According to the present invention, an automotive body transferred by afeeding device is supported by a supporting device at a wheel attachmentposition, in which a hub is reoriented on the basis of a robotreference, and then hub bolts are phased and the hub is positionallydetected. Thereafter, a wheel is attached to the hub by a nut runnerinstalled on or separate from a robot.

According to the present invention, there is provided an automatic wheelattachment apparatus for attaching a wheel to a wheel attachment memberof an automotive body, the wheel attachment member having a wheelattachment surface with wheel attachment bolts thereon, the automaticwheel attachment apparatus comprising a reorienting device forreorienting a wheel attachment surface of the wheel attachment member, aphasing device for phasing the wheel attachment bolts, the phasingdevice being movable longitudinally and vertically of the automotivebody to bring the wheel attachment member and the phasing device intocentral alignment with each other, a detecting device for detecting theamount and direction of movement of the phasing device, a nut runner forfastening the wheel to the wheel attachment member while the center ofthe wheel attachment member as detected by the detecting device is beingheld in alignment with the center of the wheel, and at least thereorienting device, the phasing device, and the detecting device beingcombined in a single robot.

The reorienting device, the phasing device, and the detecting device aremounted in one portion of the robot, and the nut runner is mounted inanother portion of the robot, the portions of the robot being supportedon a common shaft, the robot being arranged such that one of theportions confronts the wheel attachment member by rotating the shaft.

The phasing device comprises a pair of phasing fingers movable towardeach other with the wheel attachment bolts therebetween, and a mechanismfor releasing the wheel attachment bolts from dead points of the phasingfingers, the mechanism including a rotatable tube rotatable about thecenter of the phasing device, and engaging members held by the rotatabletube for engaging the wheel attachment bolts, the engaging members arerotatable with the rotatable tube and movable toward the wheelattachment member at respective speeds selected such that the engagingmembers traverse the dead points of the phasing fingers while theengaging members are being positioned so closely to the wheel attachmentmember as to engage the wheel attachment bolts.

The nut runner comprises a plurality of sockets for holding nuts to betightened over the wheel attachment bolts, a plurality of motors forrotating the sockets respectively, a plurality of drive shafts coupledto the motors, respectively, and a plurality of universal jointsconnecting the sockets and the drive shafts while allowing the socketsto be tilted with respect to the drive shafts, the universal jointsbeing movable axially of the drive shafts to allow the sockets to beretracted under reactive forces produced when the nuts engage the wheelattachment bolts.

The automatic wheel attachment apparatus also includes a wheel grippingdevice cooperating with the nut runner, the wheel gripping devicecomprising at least three cylinders independently actuatable to produceequal forces, a plurality of fingers coupled respectively to thecylinder units for pressing engagement with an outer tire of the wheelwhich is pre-positioned, and fixing means for keeping the fingers inpressing engagement with the tire.

The automatic wheel attachment apparatus further includes a wheelpositioning device cooperating with the wheel gripping device, the wheelpositioning device comprising a head vertically movably supported belowthe wheel which is transferred in horizontal attitude, a rotatablemember rotatably disposed in the head, a centralizer disposed in adistal end of the rotatable member and fittable into a central hole of awheel center of the wheel in response to upward movement of the head, aclamp member for engaging the wheel center while the centralizer isfitted in the central hole, and a pin mounted on the head and engageablein a bolt attachment hole in the wheel center when the bolt attachmenthole reaches a prescribed position upon rotation of the wheel by therotatable member.

The above and further objects, details and advantages of the presentinvention will become apparent from the following detailed descriptionof a preferred embodiment thereof, when read in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an automatic wheel attachment apparatusincorporating robots according to the present invention;

FIG. 2 is a side elevational view of the automatic wheel attachmentapparatus, with an automotive body being viewed in front elevation;

FIG. 3 is a front elevational view of the automatic wheel attachmentapparatus, with the automotive body being viewed in side elevation;

FIG. 4 is a vertical cross-sectional view of a wheel positioning device;

FlG. 5 is a plan view of the wheel positioning device;

FIG. 6 is a side elevational view, partly in cross section, of anautomotive body supporting device;

FIG. 7 is a bottom view of a floating table;

FIG. 8 is a front elevational view of a hub reorienting device and a hubbolt phasing device on a wheel attachment robot;

FIG. 9 is a side elevational view of the hub reorienting device and thehub bolt phasing device as viewed in the direction of the arrow IX inFIG. 8;

FIG. 10 is a rear elevational view of the robot;

FIG. 11 is a fragmentary side elevational view of the robot as viewed ina direction opposite to the direction in which FIG. 9 is viewed;

FIG. 12 is a cross-sectional view of the hub bolt phasing device asviewed in the direction of the arrow XII in FIG. 8;

FIG. 13 is a front elevational view showing the manner in which the hubbolt phasing device operates;

FIGS. 14 and 15 are fragmentary views of a mechanism for operating thehub bolt phasing device;

FIGS. 16(A) through 16(C) are plan views explaining the principle ofangularly correcting or reorienting hubs;

FIG. 17 is a fragmentary bottom view of a wheel gripping device;

FIG. 18 is a fragmentary side elevational view of the wheel grippingdevice;

FIG. 19 is a cross-sectional view of the wheel gripping device as viewedin the direction of the arrow XIX in FIG. 18;

FIG. 20 is a view, partly in cross section, of a gripper of the wheelgripping device;

FIG. 21 is a cross-sectional view of a nut runner;

FIG. 22 is a partly cross-sectional view taken along line XXII--XXII ofFIG. 21; and

FIGS. 23(A) through 23(C) are cross-sectional views showing the mannerin which a nut held in a socket of the nut runner is axially alignedwith a hub bolt.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIGS. 1 through 3, an automatic wheel attachment apparatus 1comprises a plurality of devices, i.e., a conveyor device 3 FIGS. 1 and2) for delivering Wheels W in horizontal attitude to an automotive body2, wheel positioning devices 36 (FIGS. 1 through 3) each for positioningthe center of a delivered wheel W and for phasing hub bolt attachmentholes of the Wheel W, an intermittent feeding device 4 forintermittently transferring the automotive body 2 to a wheel attachmentposition and for transferring the automotive body 2 with wheels Wattached to a next processing station, a supporting device 5 (FIGS. 2and 3) for floatingly supporting the automotive body 2 in the wheelattachment position, and robots 100 each for effecting various modes ofoperation ranging from the positioning of a wheel attachment member orhub 6 on the automotive body 2 to the attachment of a wheel W to the hub6. 6 These various devices of the automatic wheel 7 attachment apparatus1 will be described below in detail.

The conveyor device 3 comprises a main conveyor 30, subconveyors 31branched perpendicularly from the main conveyor 30, and subconveyors 32branched perpendicularly from the subconveyors 31 and extendinglaterally to the automotive body 2. Each of the conveyors 30, 31, 32 hasa number of longer rollers 33 and a number of shorter rollers 34positioned at branched areas for changing the direction of travel ofwheels W. When four wheels W, for example, are delivered on the mainconveyor 30, they are separated into two's which are fed onto thesubconveyors 31, from which the wheels W are transferred onto thesubconveyors 32, respectively.

The wheels W transferred onto the respective subconveyors 32 are thensupplied to the respective wheel positioning devices 36 which arelocated adjacent to the ends of the subconveyors 32. Each of the wheelpositioning devices 36 positions the center of the wheel W and phaseshub bolt insertion or attachment holes of the wheel W. Thereafter, thewheel W are held by the robots 100 and attached thereby to therespective hubs 6 of the automotive body 2.

The wheel positioning device 36 will be described With reference toFIGS. 4 and 5, the wheel positioning device 36 is disposed betweenlaterally spaced rollers 35 of the subconveyor 32. The rollers 35 aresupported on respective columns 51 on which a base 53 of the wheelpositioning device 36 is vertically movably mounted.

The base 53 is vertically movable by a cylinder unit 54 and has an upperportion to which a head 55 is secured. A vertical hollow rotatable shaft56 extends centrally through the head 55 and is rotatable by a motor 57mounted on a lower portion of the head 55. The hollow shaft 56 has onits upper end a centralizer 58 projecting upwardly from the uppersurface of the head 55. A rod 59 extends through the centralizer 58 andthe hollow shaft 56 and is rotatably coupled through a joint 61 to acylinder unit 60 mounted on the base 53. The rod 59 is thus verticallymovable in the hollow shaft 56 by the cylinder unit 60. A plurality ofradial clamp fingers 63 are movably supported on an upper head 62disposed in the centralizer 58 of the rod 59. The clamp fingers 63extend respectively through inclined holes 64 defined in an upper endportion of the hollow shaft 56 and project out of the shaft 56. Pins 65are disposed in the respective inclined holes 64 and engage respectivelyin slots 66 defined in the respective clamp fingers 63.

When the rod 59 is lowered by the cylinder unit 60, the clamp fingers 63project out of the inclined holes 64 into abutment against the innersurface of a central hole 13 of the wheel center 11 of the wheel Wthereby to secure the wheel W to the shaft 56.

Four positioning pins 67 which are equally angularly spaced around theshaft 56 are disposed in the head 55. The positioning pins 67 arenormally urged by springs 68 to move upwardly so that the upper ends ofthe pins 67 project upwardly beyond the upper surface of the head 55.

The wheel positioning device 36 thus constructed operates as follows:

The wheel W which has been delivered from the main conveyor 30 and thesubconveyor 31 onto the subconveyor 32 is stopped and held by holderarms 69 (FIG. 1). At this time, the head 55 of the wheel positioningdevice 36 is positioned downwardly of the rollers 35.

Then, the cylinder unit 54 is actuated to bring the centralizer 58 onthe upper end of the hollow shaft 56 into the central hole 13 of thewheel W, which is then lifted off the rollers 35 by the head 55. If thepositioning pins 67 enter the hub bolt attachment holes 12 of the wheel11 when the wheel W is lifted, the hub bolt attachment holes 12 haveproperly been phased. However, the hub bolt attachment holes 12 and thepins 67 are usually out of alignment, and hence the upper ends of thepositioning pins 67 engage the lower surface of the wheel center 11 butdo not enter the hub bolt attachment holes 12.

The cylinder unit 60 is operated to lower the rod 59. The clamp fingers63 are pulled out and spread to cause their distal ends to engage theinner surface of the central hole 13 of the whee1 11 for thereby fixingthe wheel W to the shaft 56. Then, the motor 57 is energized to rotatethe hollow shaft 56 through meshing gears 70, 71 to rotate the wheel Wuntil the hub bolt attachment holes 12 and the positioning pins 67 arealigned with each other, whereupon the positioning pins 67 project intothe respective hub bolt attachment holes 12 under the resiliency of thesprings 68. Upon detecting the insertion of the positioning pins 67 intothe hub bolt attachment holes 12, the motor 57 is de-energized to stopthe rotation of the shaft 56. Thereafter, the wheel W will be gripped bya wheel gripping device of the robot 100, as described later.

While in the illustrated embodiment the pins 67 are forced by thesprings 68 to project into the hub bolt attachment holes 12 of the wheel11, a cylinder unit may be employed in place of the springs 68. Morespecifically, at the time a sensor detects when the hub bolt attachmentholes 12 are positioned immediately above the positioning pins 67, themotor 57 is de-energized, and the cylinder unit is operated to insertthe positioning pins 67 into the respective hub bolt attachment holes 12to phase them.

The wheel positioning device 36 can position and phase a whee1 while itis held in a horizontal attitude. Thus, the mechanism for holding thewheel is quite simple and any conventional device for inverting thewheel is not required. Since the wheel positioning device 36 can beincorporated in the wheel conveyor, it is a space saver.

As shown in FIG. 3, the intermittent feeding device 4 has a propellingbody 41 movable by a motor or the like is movably mounted on a rail 40hung from a ceiling, and a cantilevered hanger 42 supported on thepropelling body 41, and the automotive body 2 is supported on the hanger42 for intermittent feeding along the rail 40.

The supporting device 54 which supports, in the wheel attachmentposition, the automotive body 2 that has been delivered by theintermittent feeding device 4 is illustrated in detail in FIGS. 6 and 7.

The supporting device 5 has guide receivers 81 vertically mounted on abase 80 and guide rods 83 fixed to a lifter base 82 and verticallymovably inserted through the guide receivers 81. A cylinder unit 84fixed to the base 80 has a rod 85 with its upper end secured to thelifter base 82 so that the lifter base 82 can be moved upwardly anddownwardly in response to operation of the cylinder unit 84.

Air bearings 86 are disposed on the respective four corners of the uppersurface of the lifter base 82. A table 87 is placed on the air bearings86. More specifically, each of the air bearings 86 comprises a pipe 88connected to a source of compressed air and a shallow bearing seat 89mounted on the upper end of the pipe 88, the upper surface of thebearing seat 89 being closed by a smooth flat plate 91 attached to thelower surface of the table 87.

As shown in FIG. 7, the lower surface of the bearing seat 89 has front,rear, and lateral thick portions 89a extending radially outwardly fromthe pipe 88. Rollers 92 mounted on the lower surface of the smooth flatplate 91 are held against the outer ends of the front and rear thickportions 89a. Coil springs 95 are coupled between pins 93 on the fourcorners of the lower surface of the smooth flat plate 91 and pins 94disposed around the central pipe 88 of the air bearing 86 for normallyurging the smooth flat plate 91 and the air bearing 86 to be centrallyaligned when no force is applied to the smooth flat plate 91, i.e., thetable 87.

A pin 43 is affixed to the hanger 42 (shown in cross section in FIG. 6)of the feeding device 4. The table 87 has a tube 96 mounted on its frontportion, the pin 43 being inserted in the tube 96. The tube 96 has ahole 96a in which a rod 98 of a cylinder unit 97 fixed to the table 87is inserted.

When the table 87 is lifted by the cylinder unit 84, the tube 96 isfitted over the pin 43 of the hanger 42. As the pin 43 is relativelyinserted into the tube 96 for a prescribed interval an actuator 44 onthe hanger 42 operates a limit switch 90 attached to the table 87 forenabling the rod 98 of the cylinder unit 97 to project. The distal endof the rod 98 engages in a recess of the pin 43 to securely position theautomotive body 2 on the table 87. The pin 43 houses a spring 45 thereinfor dampening any shocks which are produced when the lower end of thepin 43 hits the upper surface of the smooth flat plate 91.

With the automotive body 2 fixed to the table 87, the bearing seats 89of the air bearings 86 are supplied with compressed air. Since the uppersurfaces of the bearing seats 89 are closed by the respective smoothflat plates 91, the table 87 is movably supported in a horizontal planeon the air bearings 86. Inasmuch as the rollers 92 fixed to the smoothflat plates 91 are held against the front and rear thick portions 89a ofthe air bearings 86, however, the table 87 is floatingly supported whilebeing permitted to move only in the transverse direction of theautomotive body 2. This floating support of the automotive body 2 makesit possible to eliminate any transverse positional error of the hub 6 onone side of the automotive body 2 and also to eliminate any angularerror of the hub 6 on the other side of the automotive body 2, asdescribed later on.

Each of the robots 100 will hereinafter be described in detail.

As illustrated in FIGS. 2 and 3, the robot 100 is supported on base 101which is movable by a cylinder unit 102 in the longitudinal direction ofthe automotive body 2. A post 103 is vertically mounted on the base 101,and a box 104 housing a motor and other parts therein is mounted on theupper end of the post 103, the box 104 is vertically movable by acylinder unit 105, the box 104 supporting a shaft 106 rotatable by themotor in the box 104. The shaft 106 supports thereon a unit A forreorienting the hub 6 and phasing the hub bolts, and a unit B forholding the wheel W and attaching the wheel W to the hub 6, the units A,B being angularly space 90° about the shaft 106. The unit B isvertically movable by a cylinder unit 107.

Upon rotation of each of the shafts 106 through 90° in the direction ofthe respective arrows in FIG. 2, the unit A which has completed thereorientation of the hub 6 and the phasing of the hub bolts is turnedupwardly away from the hub 6, and the unit B carrying the wheel W isangularly moved up to the hub 6.

The unit A will first be described with reference to FIGS. 8 through 16.The unit A comprises a device 200 for reorienting the hub 6 and a device300 for phasing the hub bolts. As shown in FIGS. 8 and 9, thereorienting device 200 includes a cylinder unit 202 mounted laterally ona support plate 201 and having a rod 203 fixed to a plate 205 slidablysupported on two guide rods 204, with a pair of reorienting bars 206attached to the plate 205. As shown in FIG. 8, the reorienting bars 206are progressively spread away from each other, and movable toward andaway from the hub 6 by the cylinder unit 202 independently of thephasing device 300.

The process of reorienting the hub 6 with the correcting device 200 willbe described also with reference to FIGS. 16(A) through 16(C). Theprocess of reorientation of the hub 6 is to control the hub 6 so thatits positional error in the transverse direction of the automotive body2 and its angular error will fall within an allowable error range, withthe result that nuts can reliably be tightened on the hub bolts on thehub 6 by a nut runner, described later.

FIG. 16(A) shows in plan view the relationship between a front portionof the automotive body 2 that has been fed by the feeding device 4 andthe reorienting devices 200. In the position of FIG. 16(A), thereorienting bars 206 of the lefthand and righthand reorienting devices200L, 200R are spaced from the lefthand and righthand hubs 6L, 6R. Thehubs 6L, 6R which are not yet reoriented are positionally displaced x mmfrom their original position in the transverse direction of theautomotive body 2, and are angularly displaced y°. The hubs 6 are alwayssubjected to a positional error and to being angularly displaced whenthe hub 6 is installed on a knuckle or during transfer of the automotivebody 2. If one of the hubs, e.g., the righthand hub 6R, had a positionalerror and an angular error in a concentrated manner, then such combinederrors are so large that phasing fingers 317, 319 of the phasing device300 may not engage hub bolts 60 or nuts may not be tightened by a nutrunner 500.

According to the present invention, the reorienting bars 206 of one ofthe reorienting devices 200R can Project to a fixed extent, whereas thereorienting bars 206 of the other reorienting device 200L can project toan extent which is Possible. More specifically, the reorienting bars 206of the righthand reorienting device 200R project a fixed distance towardthe hub 6R and then stops, and the reorienting bars 206 of the lefthandreorienting device 200L project until they abut against the hub 6L andare stopped thereby.

As shown in FIG. 16(B), the reorienting bars 206 of the reorientingdevice 200R are first caused to project a fixed amount into abutmentagainst the righthand hub 6R. Since the automotive body 2 is floatinglysupported in the transverse direction, the automotive body 2 istransversely pushed by the reorienting bars 206. Now, the positionalerror and angular error of the righthand hub 6R are eliminated, and anytransversely positional error and angular error are all concentrated onthe lefthand hub 6L.

Thereafter, as shown in FIG. 16(C), the reorienting bars 206 of thelefthand reorienting device 200L are forced to project until they abutagainst the lefthand hub 6L to eliminate the angular error of the thehub 6L. However, since the righthand hub 6R is engaged by thereorienting bars 206 of the righthand reorienting device 200R, anypositional error of the lefthand hub 6L in the transverse direction ofthe automotive body 2 remains.

Subsequently, the reorienting bars 206 of the righthand reorientingdevice 200R are retracted out of engagement with the righthand hub 6R,and then the reorienting bars 206 of the lefthand reorienting device200L are retracted out of engagement with the lefthand hub 6L. When thereorienting bars 206 of the righthand reorienting device 200R areretracted first, the righthand hub 6R is subjected to an angular error.When the reorienting bars 206 of the lefthand reorienting device 200Lare thereafter retracted, no angular error is produced on the lefthandhub 6L.

After the above reorienting process, the righthand hub 6R is subjectedto an angular error only, whereas the lefthand hub 6L is subjected to apositional error only, with the result that no combined effect of theseangular and positional errors is produced on each of the hubs.Therefore, phasing fingers can reliably be brought into engagement withthe hub bolts in a subsequent phasing process, and nuts can reliably betightened on the hub bolts without fail.

The reorienting bars 206 of one of the reorienting devices 200 projectto a fixed interval, whereas the reorienting bars 206 of the otherreorienting device 200 project until they are stopped. Thus, it is notnecessary to detect how the reorienting bar 206 has projected each timethe hub is reoriented, unlike the conventional apparatus in which theamount of movement of a wheel attachment robot must be detected eachtime the hub is reoriented. Therefore, the number of control axes isreduced and the structure is simpler according to the present invention.

As shown in FIGS. 8 through 12, the hub bolt phasing device 300 includesa base assembly 301 mounted on the support plate 201 of the unit A andsupporting a pair of phasing fingers. More specifically, the baseassembly 301 comprises a first movable base 301a and a second movablebase 301b. As shown in FIGS. 9 and 11, the first 4 movable base 301aengages rails 303 attached to the support plate 201 and is movablehorizontally in a plane parallel to the wheel attachment surface of thehub 6. The second movable base 301b engages the first movable base 301athrough rails 304 and is movable vertically in a plane parallel to thewheel attachment surface of the hub 6. The first movable base 301a ishorizontally moved with quite a small force by horizontal balancingcylinders 305 (FIG. 10), whereas the second movable base 301b isvertically moved with quite a small force by a vertical balancingcylinder 306. These small forces are smaller than a force whichsubstantially deforms a resilient member such as a suspension, a rubbermount, or the like that is interposed between the hub 6 and theautomotive body 2.

As illustrated in FIGS. 10 and 11, clutch plates 307 have ends swingablysupported on the support plate 201. A cylinder unit 309 is attached tothe upper end of an arm 308 integral with the second movable base 301b.The cylinder unit 309 has a rod 309a extending through an oblong hole310 defined in the clutch plates 307 with a presser plate 311 secured tothe distal end of the rod 309a . As the movable bases 301a, 301b aremoved, the clutch plates 307 are angularly moved. When the cylinder unit309 is operated, the clutch plates 307 are sandwiched between the arm308 and the presser plate 311 to stop the movable bases 301a, 301b. Thedirection and amount of movement of the movable bases 301a, 301b aredetected by rotary encoders 312, 313.

As shown in FIGS. 9 and 13, two pairs of vertically extending upper andlower rails 315, 316 which are vertically spaced from each other aremounted by posts (not shown) on the second movable base 301b. An upperphasing finger 317 has its base 318 vertically movably mounted on theupper rails 315, and a lower phasing finger 319 has its base 320vertically movably mounted on the lower rails 316. The phasing fingers317, 319 have pairs of right-angularly spaced arms 317a, 319a,respectively, which have thin tip end portions so that when the phasingfingers 317, 319 are moved closely toward each other, the tip endportions of the arms 317a, 319a overlap each other.

The phasing fingers 317, 319 are interconnected such that they can bemoved away from each other by a mechanism (described later).

The phasing fingers 317, 319 are also in engagement with a rotatablebody 330 as well as the rails 315, 316. As shown in FIG. 12, therotatable body 330 is rotatably mounted around a tubular body 322 havingone end fixedly disposed in a circular hole 321 defined in the movablebase 301b. Curved arms 323 which are symmetrical in shape with respectto the center of rotation of the rotatable body 330 extend therefrom(only one curved arm is shown in FIG. 14). The curved arms 323 havegrooves 324, respectively, on which rollers 325 mounted on the phasingfinger bases 318, 320 are fitted. A motor 326 is mounted on a lowerportion of the movable base 301b and has a rotatable shaft 327 overwhich a semicircular gear 328 is fitted. The gear 328 is held in meshwith gear teeth 329 on the outer peripheral edge of the rotatable body330, as shown in FIGS. 12 and 15.

When the motor 326 is energized, the rotatable body 330 is angularlymoved clockwise in FIG. 8 until the curved arms 323 reach the positionindicated by the imaginary lines. During such rotation, since therollers 325 of the phasing fingers 317, 319 engage in the grooves 324 ofthe curved arms 323, the upper phasing finger 317 moves downwardly alongthe rails 315 and the lower phasing finger 319 moves upwardly along therails 316. As shown in FIG. 13, the tip ends of the arms 317a, 319a ofthe phasing fingers 317, 319 overlap each other to form a square shape.The hub bolts 60 of the hub 6 are positioned respective 14 at thecorners of the square shape. The hub bolts 60 of the hub 6 which hasbeen reoriented by the reoriented device 200 are now phased.

The center of the hub 6 after it has been reoriented and the center cfthe phasing device 300 are not necessarily aligned with each other, butmay be displaced from each other in the longitudinal and verticaldirections of the automotive body 2. At the same time that the hub bolts60 are phased, positional detection is effected in order to bring thecenter of the phasing device 300 into alignment with the center of thehub 6. More specifically, if the hub bolts 60 are phased while thephasing device 300 and the hub 6 are out of central alignment, the hubbolts 60 do not abut against the arms 317a, 319b of the upper and lowerphasing devices 317, 319 simultaneously, but one of the hub bolts 60abuts against one of the phasing fingers 317. Then, the movable bases301a, 301b supporting the phasing fingers 317, 319 are moved verticallyand laterally with small forces by the horizontal balancing cylinders305 and the vertical balancing cylinder 306. For example, if one of thehub bolts 60 first engages the upper phasing finger 317 when the motor326 is energized to move the phasing fingers 317, 319 toward each other,the upper phasing finger 317 is prevented from descending further, andthe rotatable body 330 and the lower phasing finger 319 continuouslyascend, With the first movable base 301a of the phasing device 300moving upwardly. If one of the hub bolts 60 abuts against one of thearms of the phasing fingers 317, 319, the second movable base 301b ismoved horizontally. Thus, where the hub 6 and the base assembly 301 ofthe hub bolt phasing device 300 are out of central alignment with eachother, the center of the base assembly 301 is moved into alignment withthe center of the hub 6 at the same time that the hub-bolts are beingphased. After the hub bolts have been phased, the cylinder unit 309 isoperated to rip the clutch plates 307 to fix the movable bases 301a,301b in position. Thereafter, the direction and amount of movement ofthe movable bases 301a, 301b are detected by the rotary encoders 312,313, and signals from the rotary encoders 312, 313 indicating thedetected direction and amount of movement are supplied to a control unit(not shown). The control unit then computes the accurate position of thehub 6 based on the supplied signals.

When the phasing fingers 317, 319 are moved toward each other to phasethe hub bolts 60, the hub bolts 60 which are angularly spaced 45° mayhappen to engage the dead points D.P. of the phasing fingers 317, 319,and hence the hub 6 may not rotate in either direction irrespective ofthe fact that the hub bolts 60 are out of phase.

As shown in FIG. 12, a dead-point releasing mechanism 350 is disposed inthe tubular 322 for releasing the hub bolts 60 off the dead points ofthe phasing fingers 317, 319.

The dead point releasing mechanism 350 includes a rotatable tube 352fixed to the rotatable shaft of a motor 351 and having a pair ofintegral arms 353 on its distal end, the arms 353 having through holes354 on their distal ends with engaging members 355 slidably insertedthrough the holes 354, respectively. A nonrotatable tube 356 is disposedaround the rotatable tube 352 and normally urged by a spring 357 towardthe hub 6. A cylinder rod 358 extending from a cylinder unit (not shown)has its tip end engaging the tube 356 to keep the tube 356 nonrotatableeven when the rotatable tube 352 is rotated. The tube 356 has a groove359 defined in the outer periphery thereof at its distal end, androllers 360 on the engaging members 355 are fitted in the groove 359.

The dead point releasing mechanism 350 operates as follows: When themotor 326 is energized to move the phasing fingers 317, 319 toward eachother, the motor 351 is also energized to rotate the rotatable tube 352slowly. Since the tube 356 is not rotated at this time, the rollers 360on the engaging members 355 roll in and along the groove 359 of the tube356.

Upon energization of the motor 351, the cylinder unit is operated tocause the cylinder rod 358 to move the tube 356 along the rotatable tube352 toward the hub 6. The engaging members 355 are now moved toward thehub 6 while these are being rotated by combined motion of the rotatableshaft tube, 352 as it is rotated and the tube 356 as it is moved towardthe hub 6, until finally the distal ends of the engaging members 355abut against the rear surfaces of the phasing fingers 317, 319,whereupon the tubes 352, 356 are stopped.

The speed of rotation of the tube 352 and the speed of movement of thetube 356 are selected such that during the time period in which thedistal ends of the engaging members 355 overlap the tip ends of the hubbolts 60 as viewed in side elevation as and indicated by the imaginarylines in FIG. 12, the engaging members 355 traverse the dead points D.P.of the phasing fingers 317, 319 once. With such a speed setting, even ifthe hub bolts 60 are exactly 45° out of phase, they can be displaced offthe dead points D.P. by sidewise engagement with the engaging members355 and can reliably be forced into the corners of the square shapeformed by the phasing fingers 317, 319 as they are brought together.

While the engaging members 355 are moving toward the hub 6 and rotating,the distal ends thereof may hit the tip ends of the hub bolts 60 inface-to-face relation and may not be able to engage the sides of the hubbolts 60. In this case, however, the tube 356 is resiliently retractedagainst the force of the spring 357. Such retracted movement of the tube356 is then detected, and the engaging members 355 are moved back totheir original position, after which the tube 352 is slightly rotated.Then, the above process is repeated again. Accordingly, the hub bolts 60can reliable be released from the deed points D.P. of the phasingfingers 317, 319 for phasing purposes.

As described above, the unit A of the robot 100 is composed of thedevice 200 for reorienting the hub 6 and the device 300 for phasing thehub bolts 60. The hub 6 is first reoriented by the reorienting device200, then the the hub 6 is positioned during the phasing process withthe automotive body 6 used as a reference, and the accurate position ofthe hub 6 which has been phased is computed by the control unit.Thereafter, the wheel W is placed in confronting relation to the hub 6and attached to the hub 6 by the unit B of the robot 100.

The unit B of the robot 100 will hereinafter be described.

As shown in FIGS. 2 and 3, the unit B comprises a wheel gripping device400 and a nut runner 500, which is disposed back in the center of thewheel gripping device 400.

The wheel gripping device 400 will be described with reference to FIGS.17 through 20. The wheel gripping device 400 has a pair of rails 402 ateach of the four corners of a support plate 401. A movable body 403engages each pair of rails 402 and is fixed to a cylinder unit 404 whichis actuated to move the movable body 403 along the rails 402. The rails402 in each pair extend parallel to each other. There are four cylinderunits 404 (404a-404d) secured to the support plate 401 for moving therespective movable bodies 403. In FIG. 17, only two cylinder units 404a,404b are shown in their entirety, and the other two cylinder units 404c,404d are partly illustrated. The cylinder units 404a, 404b and thecylinder units 404c, 404d have their axes parallel to each other, andthe cylinder units 404a, 404c and the cylinder units 404b, 404d havetheir axes aligned with each other. The cylinder units 404a-404d produceequal operating forces.

As illustrated in FIGS. 18 and 19, two tubes 405 are fixed to eachmovable body 403 and extend downwardly FIG. 18) perpendicularly to theaxis of the cylinder unit 404. As shown in FIG. 19, shafts 407 areinserted in the tubes 405, respectively, and normally urged by springs406 in a direction to project out of the tubes 405. The shafts 407 haveprojecting ends to which a gripper or finger 408 is secured by bolts409. The finger 408 is of a substantially triangular shape as viewed inplan as shown in FIG. 20, and has a presser plate 410 for pressingengagement with a tire 10 of the wheel W, the presser plate 410 having anumber of teeth 411 on its outer surface.

The bolts 409 are fastened to the shafts 407 at eccentric or off-centerpositions as shown in FIGS. 19 and 20. The bolts 409 are connected by aline 1₁ which extends at an angle ranging from 30° to 60° with respectto a tangential line 1₂ of the tire 10 where it is pressed by thepressed plate 410.

As shown in FIG. 18, a stack of spaced clutch plates 412 are attached atone end to each movable body 403, and are disposed at the other end inoverlapping relation to another stack of clutch plates 412 attached toanother movable body 403 within a fastening device 413 mountedtransversely centrally on the support plate 401. The movable bodies 403with their clutch plates 412 held in overlapping relation as describedabove are associated with the cylinder units 404 having aligned axes.More specifically, the clutch plates 412 of the movable body 403 whichis moved by the cylinder unit 404a are positioned in overlappingrelation to the clutch plates 412 of the 16 movable body 403 moved bythe cylinder unit 404c whereas the clutch plates 412 of the movable body403 which is moved by the cylinder unit 404b are positioned inoverlapping relation to the clutch plates 412 of the movable body 403moved by the cylinder unit 404d.

Each of the fastening devices 413 is operated by a cylinder unit 414.When the cylinder unit 414 is not actuated, the overlapping clutchplates 412 are slidable against each other, and the movable bodies 403are movable along the rails 402 by the cylinder units 404. When thecylinder unit 414 is actuated to cause the fastening device 413 to pressthe overlapping clutch plates 412 against each other, the movable bodies403 are thereby securely fixed. Thus, after the cylinder units 404 havebeen operated to cause the fingers 408 to hold the tire 10 of the wheelW, the cylinder units 414 are actuated to lock the wheel W on the wheelgripping device 400.

In operation, the cylinder unit 105 (FIGS. 2 and 3) f each robot 100 isoperated to lower the unit B of the robot 100 to the wheel positioningdevice 36, and then the cylinder units 404a-404d are actuated to gripthe tire 10 of the wheel W under equal forces at four points on the tire10.

Since the tire 10 is gripped with equal forces at plural positionsthereon, the central position of the wheel W remains unchanged. In theconventional wheel gripping device, only one cylinder unit is actuated,and its movement is transmitted through a link mechanism to respectivegripping fingers which grip the tire of a wheel 18 by depressing thesame to equal depths. However, the tire is not uniform in thickness andhas different thicknesses at localized areas. If the tire area engagedby one finger is thick and the tire area engaged by another finger isthin, then the thick tire area produces a larger repelling force whereasthe thin tire area produces a smaller repelling force when they pushedto equal depths by the corresponding fingers. In as much as the wheel isheld by the fingers only, the center of the wheel is displaced until therepelling forces from the tire become equalized.

As a result, the center of the nut runner and the center of the wheelare thrown out of alignment, and nuts cannot be tightened. The nutrunner and the wheel gripping device cannot therefore be combined witheach other.

According to the depicted embodiment of the present invention, however,the fingers 408 are attached respectively to the cylinder units404a-404d so that the fingers 408 are pulled under equal forces.Consequently, the tire 10 of the wheel W can be gripped such that, evenif the tire 10 has areas of different thicknesses, the thick tire areais depressed to a lesser degree and the thin tire area is depressed to alarger degree. The center of the wheel W which has once been positionedis thus never displaced. The wheel gripping 400 and the nut runner 500may be combined together in the unit B of the robot 100 for allowingnuts to be reliably tightened on the hub bolts.

After the wheel W has been gripped by the wheel gripping device 400while the wheel center is being kept in positional alignment, thecylinder unit 105 is actuated again to lift the unit B and the shaft 106is turned 90° to cause the unit B to face the hub 6 while the hub 6 andthe wheel W are being kept in central alignment with each other. Then,the cylinder unit 107 is operated to move the wheel gripping device 400toward the hub 6 until the hub bolts 60 are inserted into the hub boltinsertion holes of the wheel W held by the wheel gripping device 400.Nuts 502 held in respective sockets 501 of the nut runner 500 see FIG.17) are tightened on the hub bolts 60 by rotating the sockets 501 tocomplete the attachment of the wheel W to the hub 6.

As shown in FIG. 17, the nuts 502 are tightened by rotating the sockets501 counterclockwise, for example. When all of the sockets 501 are beingrotated counter-clockwise, clockwise, the nut runner 500 is subjected toa force tending to rotate the nut runner 500 counterclockwise as awhole. The wheel W is then turned bodily by such a force, exerting anundue force to the hub 6.

To eliminate the above problem, the finger 408 is shaped and the finger408 is attached to the shafts 407 as follows: The line 1₁interconnecting the bolts 409 and the line 1₂ tangential to the tire 10where it is pressed by the presser plate 410 form the prescribed angle,as described above. When the wheel W tends to rotate counterclockwiseupon counterclockwise rotation of the sockets 501 in FIG. 17, the finger408 is turned in the direction of the arrow (FIG. 20) about anintermediate point P between the bolts 409 at the time the wheel W isslightly turned. The teeth 411 of the presser plate 410 bite into (ormore firmly engage). the tire 10, there, preventing the wheel W frombeing further turned. Therefore, no undue force is applied to the hub 6when the nuts 502 are tightened.

In the illustrated embodiment, the bolts 409 are eccentrically attachedto the respective shafts 407, and the lines 1₁, 1₂ extend at theprescribed angle to each other for enabling the teeth 411 to bite intothe tire 10 when the nuts 502 are tightened. The teeth 411 may moreeffectively bite into the tire 10 by positioning resilient members as ofrubber between the shafts 407 and the fingers 408.

The nut runner 500 will be described in detail with reference to FIGS.21 through 23. As shown in FIG. 21, the nut runner 500 has a main bodyor housing 503 accommodating therein four motors 504 (only two shown),four pairs of brackets 505, 506 (only two pairs shown) mounted on afront surface (on lefthand side in FIG. 21) of the housing 503, andtables 509 coupled by parallel links 507, 508 to the brackets 505, 506.To the links 508 closer to the center of the nut runner 500, there arefixed four sector-shaped pinions 510, respectively, meshing with asingle rack 511 which is operated by a cylinder unit 512 positionedbetween the motors 504.

Guide rods 513 are mounted respectively on the tables 509. Cases 515 areslidably mounted respectively on the guide rods 513 with springs 514disposed around the guide rods 513 between the cases 515 and tables 509.

The motors 504 have rotatable output shafts coupled respectively todrive shafts 517 through constant-velocity universal joints 516. Otherconstant-velocity universal joints 518 are splined to the drive shafts517, respectively, so that the constant-velocity joints 518 arerotatable with the drive shafts 517 and axially movable with respect tothe drive shafts 517. The constant-velocity joints 518 are disposed inthe respective cases 515, with the socket 501 coupled to the distal endthereof.

Each of the sockets 501 is rotatably supported in a tubular bearingmember 519 having a magnet for magnetically attracting a nut suppliedfrom an automatic nut feeder. The bearing member 519 is supported on thecase 515 by four leaf springs 520 which are located in upper, lower, andlateral positions. The leaf springs 520 have distal ends supporting therear end of the bearing member 519 to center the bearing member 519. Thelower leaf spring 520 is held in overlapping relation to another leafspring 521, and attached therewith to the case 515. When the nut runner500 is moved toward the hub 6, the nut 502 held in the socket 501 abutsagainst the tip of the hub bolt 60, and the socket 501 is moved inwardly(to the right in FIG. 21). At this time, the socket 501 is released fromthe support by the four leaf springs 520. The leaf spring 521 serves tohold the socket 501 from below to prevent the same from tumblingdownwardly.

A single coil spring 523 is disposed around the constant-velocity joint518 between the front end of the case 515 and a spring seat 522. A ballbearing 524 is positioned between the spring seat 522 and an innersurface of the socket 501 for allowing the socket 501 to move under avery small force substantially in the radial direction of the case 515.

For tightening nuts 502 with the nut runner 500, the nuts 502 aresupplied to the nut runner 500, and then the shaft 106 is turned 90°from the position of FIGS. 2 and 3 until the unit B faces the hub 6. Atthis time, the unit B is controlled by the control unit (not shown) suchthat the unit B confronts the hub 6 at the exactly central positionthereof which has been computed by the control unit based on the outputsignals from the rotary encoders 312, 313 of the hub bolt phasing device300.

Then, the wheel gripping device 400 is moved toward the hub 6 to insertthe hub bolts 60 into the respective hub bolt attachment holes 12 of thewheel center 11 of the wheel W, and thereafter the nut runner 500 isadvanced toward the hub 6. The nuts 502 are then tightened over therespective hub bolts 70 by energizing the motors 504.

The hub bolts 60 may not necessarily extend perpendicularly to theattachment surface of the hub 6, but may be inclined at an angle rangingfrom 2° to 3°. For example, the axis 1₃ of the hub bolt 60 may not bealigned with the axis 1₄ of the nut 502, as shown in FIG. 23(A). If thenut 502 were tightened in this condition, it would not properly bethreaded over the hub bolt 60 or would not be removed from the socket501 after being tightened over the hub bolt 60.

To overcome the above problem, the axis 1₃ of the hub bolt 60 and theaxis 1₄ of the nut 502 are brought into alignment with each other asfollows: The socket 501 is rotated from the position of FIG. 23(A) whilethe nut runner 500 is moved toward the hub 6. When the inner surface ofthe nut 502 hits the tip end of the hub bolt 60 and the socket 501 smoved back by reactive forces from the hub bolt 60 as shown in FIG. 23B), the socket 501 is moved substantially radially of the case 515 sincethe resistance to the rolling movement of the ball bearing 524 betweenthe spring seat 522 and the socket 501 is very small. Thus, the axes 1₃,1₄ are brought into alignment with each other as illustrated in FIG.23(B).

Then, as shown in FIG. 23(C) , the nut runner 500 is moved toward thehub 6 to move the socket 501 relatively backwards further, whereupon thesocket 501 is tilted against the flexural rigidity of the spring 523 tocause the axes 1₃, 1₄ to be completely aligned with each other. For theaxes 1₃, 1₄ to be completely aligned with each other, the socket 501must be moved in any of vertical and lateral directions from theposition of FIG. 23(B), and such movement of the socket 501 is allowedby the bending of the leaf springs 520. The rotation of the motor 504during this time is transmitted through the constant-velocity joint 516,the drive shaft 517, and the constant-velocity joint 518 to the socket501 to tighten the nut 502 over the hub bolt 60.

Where wheels W are to be attached to an automotive body of a differenttype with different distances between hub bolts 60, the cylinder unit512 in the housing 503 is operated to move the rack 511 in one directionor the other. The pinions 510 are turned to angularly move the parallellinks 507, 508 to move the tables 509 toward or away from each other.Thus, the socket 501 supported on the tables 509 by the guide rods 513and the cases 515 are also moved toward or away from each other untilthey are properly aligned with the hub bolts 60.

As described above, the bearing member 519 of the nut runner 500 isfloatingly supported so that when the nut 502 is pressed against the hubbolt 60, the bearing 519 can be varied in position and angle to enablethe nut 502 to be aligned with the hub bolt 60 under a small force.Specifically, the bearing 519 is moved first to correct axialmisalignment of the nut 502 and the hub bolt 60 and then to correctangular deviation between the nut 502 and the hub bolt 60. Therefore,the nut 502 will properly be tightened over the hub bolt 60 withoutbiting threaded engagement, and will smoothly be removed from the socket501 after it is tightened over the hub bolt 60.

With the present invention, since the reorienting device for reorientingthe hub, the phasing device for phasing the hub bolts, and the devicefor detecting the position of the hub are incorporated in one robot, theapparatus is integrated and the time required to attach wheels to anautomotive body is shortened. With the various devices combined in onerobot, the hub reorientation, the hub bolt phasing, and the positionaldetection can be performed without rotating the robot, and the wheelattachment process can be effected highly efficiently.

The apparatus can be more integrated and the wheel attachment time canbe reduced by incorporating the nut runner and the wheel gripping devicein the robot.

Although there has been described what is at present considered to bethe preferred embodiment of the present invention, it will be understoodthat the invention be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all aspects as illustrative,and not restrictive. The scope of the invention is indicated by theappended claims rather than by the foregoing description.

What is claimed:
 1. A phasing device for phasing wheel attachment bolts,comprising a pair of phasing fingers movable towards each other withwheel attachment bolts on a wheel attachment member therebetween, and amechanism for releasing said wheel attachment bolts from dead points ofsaid phasing fingers, said mechanism including a rotatable tuberotatable about a central portion of said phasing device, and engagingmembers held by said rotatable tube for engaging said wheel attachmentbolts, said engaging members being rotatable with said rotatable tubeand movable toward said wheel attachment member at respective speedsselected such that said engaging members traverse the dead points of thephasing fingers while the engaging members are positioned enough to saidwheel attachment member so as to be able to engage said wheel attachmentbolts.
 2. A method of phasing wheel attachment bolts, comprising thesteps of:moving a pair phasing fingers toward each other with the wheelattachment bolts located therebetween; rotating engaging members whilemoving the engaging members toward the wheel attachment bolts engagingthe wheel attachment bolts with the engaging members for therebyremoving the wheel attachment bolts from areas corresponding to deadpoints of the phasing fingers by said rotation of said engaging member;thereafter pressing the phasing fingers against the wheel attachmentbolts, thereby phasing the wheel attachment bolts.
 3. A method accordingto claim 2, including when the amount of movement of said engagingmembers toward said wheel attachment bolts is smaller than a prescribedamount, moving said engaging members back to their original position,and then slightly rotating the engaging members and thereafter movingsaid engaging members towards said wheel attachment bolts while rotatingsaid engaging members.